The invention relates to the field of haematological analyses, and more specifically to the preparation of blood smears on plates.
In this particular field, it is known to deposit a drop of a blood sample on a plate, such as a glass plate for analysis under a microscope, and to spread this drop on the plate in order to produce what is known as a blood smear. The latter is then dried, then coloured by at least one appropriate reagent, in order to permit subsequent analysis under the microscope. In fact, analysis of plates of this type makes it possible to determine the composition of the blood sample concerned, which is of great importance for the diagnosis of specific pathologies.
Blood smears of this type can be prepared by automated devices, which, on the basis of a stock of new plates, carry out a multiplicity of operations of depositing and spreading of blood on plates and miscellaneous subsequent processing operations such as drying and colouring. The plates thus processed are then collected in appropriate containers.
Devices of this type are already known, in particular from publications U.S. Pat. No. 4,034,700, EP 0 735 358, and WO 97/18457.
However, automatic preparation of plates of this type poses various problems, in particular concerning spreading of the blood, which must be perfectly controlled in order to obtain regular distribution of the cells on the plate, irrespective of the quantity of cells present in the blood.
It is also necessary for this spreading to be carried out without any risk of contamination from a previous spreading operation.
Another problem is associated with handling of the plates themselves, which consist of thin, relatively fragile glass plates, which also have the disadvantage that they have a natural tendency to adhere to one another when they are new, and are disposed in stacks.
Yet another problem is associated with the use of toxic products in order to carry out the operations of colouring of the plates, from bottles of reagents, and also with the rinsing operations which are carried out by solvents. It is thus essential to be able to prevent the migration of toxic vapours.
All of these problems, and others, have not yet been solved satisfactorily by the devices for preparation of bloods smears which are known according to the prior art.